Resurrecting a 38 Year Old Motorcycle

About: I enjoy taking a pile of junk and making something unusual out of it. I like wheeled vehicles, and currently own two motorcycles, two electric bikes that I've built, and an electric scooter pushed by a soc...
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I was looking for a fall project, and decided to take on resurrecting a 1972 Honda SL125 that had been sitting in storage for 18 years. The bike had been stored near some swimming pool chemicals and fertilizer, and every metal surface was either rusted (steel) or oxidized (aluminum). The bike would not have been a suitable candidate for restoring to original, but was a good candidate for "resurrecting" as a rider.

The good news was that the motor and transmission was in good shape, with 9,000 miles on the odometer. The clutch plates were stuck, but about an hour of rocking the bike back and forth with the bike in gear and the clutch lever pulled finally broke them free.

The carburator was beyond redemption -- the idle circuit and air bleed were too corroded to rebuild, but an ebay carb took care of that problem. I also replaced the horn, the ignition switch, and one of the rear shocks -- again, using ebay.

So, my instructable is focused mainly on rust and corrosion removal, which took the better part of two months to complete.

Supplies:

Step 1: Removing Stuff

I began by removing the seat, gas tank, fenders, exhaust system, side covers, and the rear view mirrors.

The seat was held on by two nuts, and once removing these I simply lifted up the rear of the seat and pulled the front loose from its bracket. With the seat removed, the gas tank (after removing the fuel line) pulled free from its front bracket.

The front fender was held by three bolts, which I wound up having to twist off (too corroded to come loose, even with plenty of penetrating oil). I drilled out these broken bolts.

The rear fender was held on by four bolts, and once removed I could get to the bolts that held the tail light/license bracket. The wire for the tail light unit simply unplugged from the wiring harness.

The exhaust system surprisingly came free without breaking any of the studs that held it on.

The side covers were designed to simply pop on and off, so they came off easily, and the rear view mirrors unscrewed from their handlebar mounts.

Throughout all of the disassembly process I carefully kept track of all loose parts by putting them in labeled sandwitch bags.

Step 2: Preparing the Frame

I began the rust removal process with the frame. I decided that since everything was highly visible on this bike, I would not need to remove the motor -- I'd just work around it.

Beginning with 120 grit shop rolls, I sanded every square inch of the frame, then switched to 220 grit. Once all rust was removed, I painted the frame with a rust stopping primer. I used a brush to apply the primer, since I had decided to paint the frame with a hammered finish enamel. I decided on using the hammered finish, since the frame was too pitted for a really smooth finish.

Step 3: Exhaust System

The exhaust system was badly rusted, but still sound. After sanding and grinding away the rust, I used an automotive high-temp primer, followed by a high-temp flat black enamel.

Because of the size of the exhaust system, I was unable to bake the paint on in my wife's oven, so I baked it by periodically running the engine for 10 minutes after the bike's fuel tank was reinstalled.

Throughout this entire "resurrection" process, all parts that had previously been chrome plated were sanded and painted, including the exhaust system. There was simply too much pitting for re-chroming.

Step 4: Tackling Rusty Rims

The rims on this project bike were in terrible shape. The front wheel was entirely coated in rust, including every spoke. Fortunately, however, this was just surface rust and pitting -- the integrity of the rims was still sound.

I started with 120 grit paper and worked my way down to 220 grit on the rims and the spokes. All-in-all I spent 7 hours sanding the front wheel and 3 hours sanding the rear wheel.

Before sanding the rims, I tried every rust-removing chemical I coudl find (including using cola!). Unfortunately, the rust was just too profound for chemical removal, so I had to do it the hard way.

Once all the rust was removed, I sprayed each wheel with primer, then the hammered finish enamel.

Step 5: Repairing the Gas Tank

The gas tank had numerous problems. First, the inside was rusty and coated with 38 years of gunk. The petcock was clogged, and the tank had four dents in it.

Using a drill bit as a hand reamer, I unplugged the galleys in the petcock, then soaked it in carb cleaner.

For the inside of the tank, I first put a handful of nuts an bolts in it along with about a quart of degreaser, plugged the inlet and outlet, then rocked the tank back and forth and up & down for about 30 minutes to loosen the crud inside. Next I used a DIY commercial cleaning coating process which entailed soaking the inside of the tank in a weak acid solution for 8 hours, then using a neutralizer, then a permanent coating.

After taking care of the tank's insides, I then began work on the part that "shows." I used bondo to fill the four dents, carefully sanding and feathering the filler to the lines of the tank. Then I applied primer, then paint.

While the finaly coat was drying, I used a small knife blade to scrape away the rust from the tank's logo, then touched up the paint on the logo with an artist's brush.

Before reattaching the logo, I applied stair tread (sort of like a rough, rubbery tape) to the sides of the tank for decoration, then screwed the logo back on each side.

I realize this is not exactly how the original looked, but remember -- this is a resurrection, not a restoration!

Step 6: Fenders, Side Covers, Miscellaneous

All removed parts were sanded, primed, and painted.

The side covers were the only plastic items on the bike, and befrore painting I fixed a couple of cracks in one of them using hot glue (on the back side). Then I sanded, primed, and painted them just like the metal parts. The logos on the side covers were cleaned up and touched up.

While parts were drying, I recovered the seat with a seat cover I bought off of ebay.

Step 7: Reassembly

The reassembly basically involved doing everything in reverse. It is at this point when I was really glad I took the time to put all loose parts in labeled sandwitch bags!

Step 8: New Carb

I finally decided to replace the carburator. I just couldn't get it adjusted due to the bad corrosion that had built up. A new carburator from ebay made the bike run like new.

Step 9:

The project is finished! I spent quite a bit of time on this bike (7 hours just sanding one wheel!), but very little money. All-in-all I think I spent around $300 on parts and supplies.

I'm not a motorcycle mechanic, but am reasonably handy with tools. When I began this project I purchased a Clymer manual, which I found indespensible.

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168 Discussions

I have a 1974 Honda CB360 that was going to be rebuilt in 1981 but wasn't done. I all in parts, engine is still intact (not in pieces). Someone told me the engine do not have to be taken apart. Carburator needs new kit. Is this true? It's been stored all these years, no water hitting it, etc....

I have a 1973 SL350k2 barn find I'm considering on restoring. This is an inspiring project, even if the one I am looking at is not salvageable for riding (i.e. not sure if the engine is viable) ... for parts, perhaps.

I have sent an email if you would like to feed me some input on your total estimated time on the project.

BTW: Did you pay anything for the barn find bike before you started the project?

Thankyou for the information on this topic! I have been considering resurrecting or restoring an old Honda CB500T that has part of it scattered across my families land. For instance, the frame is in a deep gully, but the motor (Which runs) is in my dads shop. The frame is quite rusted from sitting outside for roughly 30 years, though parts for old CB500T's are extremly inexpensive! Anyways, thankyou again for the great description!

Should have tried "Metal Rescue". It will remove rust that heavy just by soaking for a few hours. Can get it at Home Depot or even Walmart. Comes in qt., Gal., and 5- gallon buckets. google it and watch their videos.

how did you apply the enamel finish? spray or brush? sorry if it's a bit of a noob question, but I just dug up an old motorcycle in a similar condition to yours, and I don't want to go through all of the trouble of removing the motor and stuff to repaint the frame.

Hey just wondering what carb setting did you use? I am trying to fine tune my carb yet everyone insists 2 turns out from seated, which I can't get the bike to even start, much less run very well. I am currently running extremely lean to where the air/fuel setting is almost flush with the outer lip

I'm curious to know how you did the front forks. I'm restoring a 1974 XL175, and the forks have a bit of surface rust. You ended up painting yours black I see, did you have any problems with oil leaking? How did you maintain suspension without having to replace the forks altogether?

It's hard to tell from the photo, but it looks to me like the rust has eroded the metal in some places. If it's just light surface rust, you might be ok. If it has actually eaten into the structure, I wouldn't risk it.